Hydrodynamic torque transmitting device, with molded plastic rotor



Aug. 3l,l 1943. R L sMlRL 2,328,175

HYDRODYNAMIC TORQUE TRANSMITTING DEVICE WITH MOLDED PLASTIC KOTOR Filed Aug. 19, '1940 Patented Aug. 31, 1943 HYDRODYNAMIC TOBQUE TBANSMITTING DEVICE, WITH MOLDED PLASTIC ROTOB melma L snm-1, Detroit, Mich., signor to Borg-Warner Corporation, Chicago, lll., a oorpora'tion of Illinois Application august 13, 1940, serial No. 353,204

3 chims. (ci. ca -54) 'I'his invention relates to hydrodynamic torque transmitting devices for motor vehicles and the like. Hydrodynamic power transmitting devices ofthe Fttinger type are comprised of a varied driving element, a vaned driven-element and, if

torque multiplicationl is desired. a vaned stationary element al1 included in a toroidal housing. The vanes may be flat and radially disposed as in a simple coupling, or they may be intricately shaped as in the torque multiplying device. In either case, each element must be perfectly balanced to avoid vibration and undue bearing loads, and in addition, must be smooth and free of sharp corners and pockets to avoid the creation of eddy currents which adversely affect the efciency of the device.

It has been proposed to make hydrodynamic couplings -from sheet metal by forming a'. halftoroidal shell and then welding in stamped or formed vanes. This method presents serious welding problems, and a coupling so constructed is certain to have sharp comers which impair its eillciency. In addition, the speciiic weight of steel is so high that large stresses are set up in the shell as a result of centrifugal force. It is readily apparent that to form, assemble and balance a sheet metal coupling properly entails considerable expense.

The general object of this invention is to provide a hydrodynamic device which combines increasedfefllciency of perfomance with. diminlished manufacturing cost.

In general, these objects are attained by form- Y ing at least one of the vaned rotor members of the device with thevaned portion thereof in the form of a single integral annulus of molded plastic material having smooth burnished surfaces devoid of any projections, against which maximum eillciency of iiuid action may be obtained.

In order to provide adequate torsional strength at the hub, the rotor is provided with a metallic hub the cost of which is maintained at a minimum by stamping it from heavy sheet metal. The torus portion of the rotor lis molded upon an axially extended rim flange of the hub 'which supports the adjacent region of the torus against rupture under the efl'ect of centrifugal force.

It has previously been proposed to form the nized as a major one, and it has been previously thought that an unsupported rotor of molded plastic material would not be suficiently strong for the intended DUI'POse.

In a hydrodynamic torque transmitting device such as a fluid coupling, the problem is greatly magnified owing to the large diameter of the rotor which is necessary to the transmission of ample power. The present invention involves the conception that in a fluid coupling, a rotor,

strong enough to resist rupture under centrifugal rotors of small fluid pumps of molded plastic problem of rupture of the rotor under the efl'ectL of centrifugalforce combined with the resistance of the fluid being acted upon, has been recogforce as long as it is operating in a body of iiuid, may be made of molded plastic material 'so as ton embody the advantages of increased efliciency of fluid action, without the use of reenforcing except at its inner extremity and, to this end, has as one of its objects to provide a rotor which is constructed of material having a speciic gravity near that of the fluid in which it operates.

.Other objects, the advantages and uses of the invention will become more apparent after read- -ing the following specication andclaims, and

after consideration of the drawing forming a part of the specincation, wherein:

Fig. 1 is an axial sectional view of a portion of a transmission embodying the invention;

Fig. 2 is a detailed sectional view taken on the line 2-2 of Fig. 1: and

Fig. 3 is a detailed sectional view taken on the line .3-3 of Fig. 1.

For purposes'of illustration this invention will be described with reference to a hydrodynamic coupling, it being understood that the invention is applicable to hydrodynamic torque converters and other similar devices as well.

I have shown in theldrawing a portion of a transmission including a housing 8, a drive shaft 9, which may be the rear extremity of an engine crank shaft, a driven shaft Il), leading to the gearing of the transmission, and a hydraulic coupling including a housing II, vone-half of which constitutes an impeller I2 and a runner I3 adapted to be driven from the impeller I2 by a suitable body of fluid, such as oil, circulated-between the two.

The housing II may comprise two heavy sheet metal stampings Il and I5 respectively, the stamping II carrying the impeller pockets I6 and the stamping I5 forming, together with the impellerV I2, anannular chamber I1, in which the runner I3 is received. The stamping I4 may be reenforced in its'inner. region by a ring Il welded thereto as at 2l, and is secured as by bolts 2| to the flange 22 ofthe driving shaft 9. 'I'he stamping I5 is welded as' at 23 to the periphery of the stamping I4 and has secured to its innerLreglon as by means of screws 24 a ring 25 having an axial flange 26 which cooperates with a packing ring 21 for sealing the chamber I1 around the shaft III.

polish, which, together with the absence ofpro-` jections on such surfaces provides for a very smooth flow of fluid through the pockets 44, increasing the efficiency of the coupling. l The inner region of the wall 28 is thickened as at 3I. Embedded in the thickened region 3I is the rim 32 of a ring 33 which is riveted as'at 34 to the flange 35 of a hub 36. 'I'he hub 36 is internally splined to receive the splined section 31 of the driven shaft III.-l

'I'he rim 32 .supports the inner region 3| of the wall 28 against rupture under the eifect of centrifugal force.' 'I'he remainder ofthe wall 28 is supported against rupture by the gradual thickning of the wall toward the linner region 3I yand the bridging of theinner and outer regions of the wall by the radial vanes 29.

When operating in a fluid, the centrifugal force actingagainst the runner may be determined by the amount of centrifugal force thatwould be developed by the runner operating in air, minus the centrifugal force that would be developed by a runner of the same dimensions having the same weight as the quantity of fluid that is displaced by the runner. To state it somewhat diiferently, the centrifugal for-ce developed in the runner is a function of the difference between the'speciiic gravity of the plastic material of which the runner is composed and the fluid in which it operates. Utilizing this principle, the invention makes it possibleto employ a material such as a phenolic thermo-setting type of molded plastic material, for example, one of the materials sold vunder the trade name Bake-Lite, Durez,

Durite, ndu-r," Makalot, Resinox, Textolite, etc., where such materialA operating in air would tend to disintegrate under the eiert of centrifugal force at the maximum speed of operation. Furthermore, I have discovered that it is possible to achieve sufficient strength in a vaned torus which is supported by reenforcing metallic structure only at its inner extremity.

'I'he impeller II may be likewise formed of molded plastic material or it may be formedof stamped sheet metal as shown. The pockets in the illustrated embodiment I6 are formed of light sheet metal, stamped to provide a semi-circular wall 40 and la radial wall 4I bridging one side of the/wall 40. Thewall 40 is spot welded as at 42 to the Wall I4 of the impeller, with the radial wall Iof the pockets across the gap between the impeller and runner and into the pockets 44 of the runner, in the outer regions thereof. Deilected radially inwa-rdly by the toroidal wall I4 4of the runner, the fluid will be discharged back into the pockets I6 of the impeller. This circulation,

which is in a clockwise direction as viewed in th upper portion of Fig. 1, is indicated -by the arrows 45.

It will be apparent that the smooth iinish of the wall 28 and vanes 29, coupled with the absence of any irregularities or projections on the surfaces, will facilitate the ow of i'luid through the pockets 44 and thereby increase the eiiiciency of the coupling. Y

Centrifugal force will maintain a substantially solid body of uid within the shell of the coupling throughout the annular region thereof occupied by the vaned portion of the runner. sult, the centrifugalforce tending to disrupt the runner, is diminished according to the ratio of the weight of the uid to the weight of the plastic material of which the runner is composed.

The invention provides a runner which is constructed of material such as the materials listed above, having a specic gravity less than two and one-half times that of the uid in which it operates. v

The strength of the material is ample to handle the torque load by using the sections ordinarily required for molding practice for exanrple, the toroidal wall of the runner may be tapered from a maximum thickness at its inner extremity to a minimum thickness in its outer region in the neighborhood of not substantially greater than 30 1,40 of the radial distance between the inner and outer extremities of the toroidal wall, and vanes may have a thickness not substantially more than $60 of said radial distance. The buoyancy principle reduces the centrifugal stress to a very reasonable ligure as shown below: f

1a. P. M.

If the steel rotor is immersed inv oil (W=7.8.9=6.9), its stress is only reduced to 26,600#/sq.'9 at 6,000 R.. P. M.

`While I have described my invention in connection with one specific embodimentlthereof, it is to be understood that this is by way of illustration and not by way of limitation, and the scope of my invention is defined solely by the appended claims.

I claim: l

.1. In a hydrodynamic power transmitting device, a housing, fluid therein, a runner operating in said uid, said runner being integrally formed 'of a molded plastic material having a specific gravity less than 21/2 times the specific gravity of the fluid, said runner includinga toroidal wall of arcuate cross section tapering from maximum thickness at its inner extremity to minimum thickness in its outer region, said minimum thickness being in the neighborhood of not substantially greater than 1/40 of the radial distance between the inner and outer extremities of said toroidal wall portion, and vanes extending between said inner and outer wall portions and integrally joined to said toroidal wall portion, said vanes having a thickness not substantially more than 60 of said radial distance.

2. A hydrodynamic power transmitting device comprising a driving housing, a vaned'impeller connected to the housing and adapted to be driven thereby, said vhousing taking the stresses produced in the impeller by reason of the rotation thereof, a rotor adapted to be rotated from the impeller, said rotor receiving no direct reinforcement against centrifugally produced stresses on the housing, and fluid substantially iilling the housing so as to submerge the greater portion of the rotor, said rotor being made' of a material having a specific gravity less than two and one-half times the speciiic gravity of the uid,

said rotor including a toroidal wall of arcuate cross section tapering in thickness from its inner to its outer extremity, having a thickness in its outer region of not substantially more than 1,40 of the radialdistance between its inner and outer extremities, and including v'anes extending from its outer to its inner extremity and integrally joined to said toroidal wall, said vanes having a thickness not substantially greater than $60 of said radial distance.

3. A hydrodynamic power transmitting device comprising a driving housing, a vaned impeller connected to the housing and adapted to be driven thereby, said housing taking the stresses produced in the impeller by reason 'of the rotation thereof, a runner adapted to be rotated from the lmpeller, said runner receiving no reinforcement against centriiugally produced stresses in the housing, and fluid substantially filling the housing so as to submerge the greater portion of the runner, said runner being made of a material having a specific gravity less than 21/2' times the speciiic gravity of the iiuid and including a toroidal wall of arcuate crossv section tapering from maximum thickness at its inner extremity to minimum thickness in. its outer region, said minimum thickness being in the neighborhood of notsubstantially'greater than 1/40 of the radial distance between the inner and outer extremities of said toroidal wall portion, and vanes extending between said inner and outer wall portions and integrally joined to said toroidal wall portion, said vanes having a thicknes not substantially more than 1,50 of said radial distance.

. RICHARD L. SLMRL. 

